PR libstdc++/77691 fix resource_adaptor failures due to max_align_t bugs

Remove the hardcoded whitelist of allocators expected to return memory
aligned to alignof(max_align_t), because that doesn't work when the
platform's malloc() and GCC's max_align_t do not agree what the largest
fundamental alignment is. It's also sub-optimal for user-defined
allocators that return memory suitable for any fundamental alignment.

Instead use a hardcoded list of alignments that are definitely supported
by the platform malloc, and use a copy of the allocator rebound to a POD
type with the requested alignment. Only allocate an oversized
buffer to use with std::align for alignments larger than any of the
hardcoded values.

For 32-bit Solaris x86 do not include alignof(max_align_t) in the
hardcoded values.

	PR libstdc++/77691
	* include/experimental/memory_resource: Add system header pragma.
	(__resource_adaptor_common::__guaranteed_alignment): Remove.
	(__resource_adaptor_common::_Types)
	(__resource_adaptor_common::__new_list)
	(__resource_adaptor_common::_New_list)
	(__resource_adaptor_common::_Alignments)
	(__resource_adaptor_common::_Fund_align_types): New utilities for
	creating a list of types with fundamental alignments.
	(__resource_adaptor_imp::do_allocate): Call new _M_allocate function.
	(__resource_adaptor_imp::do_deallocate): Call new _M_deallocate
	function.
	(__resource_adaptor_imp::_M_allocate): New function that first tries
	to use an allocator rebound to a type with a fundamental alignment.
	(__resource_adaptor_imp::_M_deallocate): Likewise for deallocation.
	* testsuite/experimental/memory_resource/new_delete_resource.cc:
	Adjust expected allocation sizes.
	* testsuite/experimental/memory_resource/resource_adaptor.cc: Remove
	xfail.

From-SVN: r271522

4 files changed, 94 insertions, 43 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 056e354..cf9d86a 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,21 @@
+2019-05-22  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/77691
+	* include/experimental/memory_resource: Add system header pragma and
+	do not define anything unless compiled as C++14 or later.
+	(__resource_adaptor_common::__guaranteed_alignment): Remove.
+	(__resource_adaptor_imp::do_allocate): If the requested alignment
+	is a fundamental alignment then either allocate directly from _M_alloc
+	or call the new _M_allocate function.
+	(__resource_adaptor_imp::do_deallocate): Likewise for deallocation.
+	(__resource_adaptor_imp::_M_allocate): New function that uses a copy
+	of the allocator rebound to a POD type with the specified alignment.
+	(__resource_adaptor_imp::_M_deallocate): Likewise for deallocation.
+	* testsuite/experimental/memory_resource/new_delete_resource.cc:
+	Adjust expected allocation sizes.
+	* testsuite/experimental/memory_resource/resource_adaptor.cc: Remove
+	xfail for Solaris x86.
+
 2019-05-21  Thomas Rodgers  <trodgers@redhat.com>
 
 	LWG 3062 - Unnecessary decay_t in is_execution_policy_v
diff --git a/libstdc++-v3/include/experimental/memory_resource b/libstdc++-v3/include/experimental/memory_resource
index a0b3063..dde3753 100644
--- a/libstdc++-v3/include/experimental/memory_resource
+++ b/libstdc++-v3/include/experimental/memory_resource
@@ -30,6 +30,10 @@
 #ifndef _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE
 #define _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE 1
 
+#pragma GCC system_header
+
+#if __cplusplus >= 201402L
+
 #include <memory>			// align, uses_allocator, __uses_alloc
 #include <experimental/utility>		// pair, experimental::erased_type
 #include <atomic>			// atomic
@@ -358,23 +362,6 @@ namespace pmr {
 	  return __val;
 	}
     };
-
-    template<typename _Alloc>
-      struct __guaranteed_alignment : std::integral_constant<size_t, 1> { };
-
-    template<typename _Tp>
-      struct __guaranteed_alignment<__gnu_cxx::new_allocator<_Tp>>
-      : std::alignment_of<std::max_align_t>::type { };
-
-    template<typename _Tp>
-      struct __guaranteed_alignment<__gnu_cxx::malloc_allocator<_Tp>>
-      : std::alignment_of<std::max_align_t>::type { };
-
-#if _GLIBCXX_USE_ALLOCATOR_NEW
-    template<typename _Tp>
-      struct __guaranteed_alignment<std::allocator<_Tp>>
-      : std::alignment_of<std::max_align_t>::type { };
-#endif
   };
   /// @endcond
 
@@ -425,14 +412,22 @@ namespace pmr {
       virtual void*
       do_allocate(size_t __bytes, size_t __alignment) override
       {
-	if (__alignment <= __guaranteed_alignment<_Alloc>::value)
+	// Cannot use max_align_t on 32-bit Solaris x86, see PR libstdc++/77691
+#if ! (defined __sun__ && defined __i386__)
+	if (__alignment == alignof(max_align_t))
+	  return _M_allocate<alignof(max_align_t)>(__bytes);
+#endif
+	switch (__alignment)
 	  {
-	    if (__bytes < __alignment)
-	      __bytes = __alignment;
+	  case 1:
 	    return _M_alloc.allocate(__bytes);
+	  case 2:
+	    return _M_allocate<2>(__bytes);
+	  case 4:
+	    return _M_allocate<4>(__bytes);
+	  case 8:
+	    return _M_allocate<8>(__bytes);
 	  }
-
-
 	const _AlignMgr __mgr(__bytes, __alignment);
 	// Assume _M_alloc returns 1-byte aligned memory, so allocate enough
 	// space to fit a block of the right size and alignment, plus some
@@ -441,21 +436,28 @@ namespace pmr {
       }
 
       virtual void
-      do_deallocate(void* __p, size_t __bytes, size_t __alignment) noexcept
+      do_deallocate(void* __ptr, size_t __bytes, size_t __alignment) noexcept
       override
       {
-	auto __ptr = static_cast<char*>(__p);
-	if (__alignment <= __guaranteed_alignment<_Alloc>::value)
+#if ! (defined __sun__ && defined __i386__)
+	if (__alignment == alignof(max_align_t))
+	  return (void) _M_deallocate<alignof(max_align_t)>(__ptr, __bytes);
+#endif
+	switch (__alignment)
 	  {
-	    if (__bytes < __alignment)
-	      __bytes = __alignment;
-	    _M_alloc.deallocate(__ptr, __bytes);
-	    return;
+	  case 1:
+	    return (void) _M_alloc.deallocate((char*)__ptr, __bytes);
+	  case 2:
+	    return (void) _M_deallocate<2>(__ptr, __bytes);
+	  case 4:
+	    return (void) _M_deallocate<4>(__ptr, __bytes);
+	  case 8:
+	    return (void) _M_deallocate<8>(__ptr, __bytes);
 	  }
-
 	const _AlignMgr __mgr(__bytes, __alignment);
-	// Use the stored token to retrieve the original pointer to deallocate.
-	_M_alloc.deallocate(__mgr._M_unadjust(__ptr), __mgr._M_alloc_size());
+	// Use the stored token to retrieve the original pointer.
+	_M_alloc.deallocate(__mgr._M_unadjust((char*)__ptr),
+	    __mgr._M_alloc_size());
       }
 
       virtual bool
@@ -467,6 +469,31 @@ namespace pmr {
       }
 
     private:
+      template<size_t _Num>
+	struct _Aligned_type { alignas(_Num) char __c[_Num]; };
+
+      // Rebind the allocator to the specified type and use it to allocate.
+      template<size_t _Num, typename _Tp = _Aligned_type<_Num>>
+	void*
+	_M_allocate(size_t __bytes)
+	{
+	  typename allocator_traits<_Alloc>::template
+	    rebind_alloc<_Tp> __a2(_M_alloc);
+	  const size_t __n = (__bytes + _Num - 1) / _Num;
+	  return __a2.allocate(__n);
+	}
+
+      // Rebind the allocator to the specified type and use it to deallocate.
+      template<size_t _Num, typename _Tp = _Aligned_type<_Num>>
+	void
+	_M_deallocate(void* __ptr, size_t __bytes) noexcept
+	{
+	  typename allocator_traits<_Alloc>::template
+	    rebind_alloc<_Tp> __a2(_M_alloc);
+	  const size_t __n = (__bytes + _Num - 1) / _Num;
+	  __a2.deallocate((_Tp*)__ptr, __n);
+	}
+
       _Alloc _M_alloc{};
     };
 
@@ -537,4 +564,5 @@ namespace pmr {
 
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
+#endif // C++14
 #endif // _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE
diff --git a/libstdc++-v3/testsuite/experimental/memory_resource/new_delete_resource.cc b/libstdc++-v3/testsuite/experimental/memory_resource/new_delete_resource.cc
index 41232b6..7dcb408 100644
--- a/libstdc++-v3/testsuite/experimental/memory_resource/new_delete_resource.cc
+++ b/libstdc++-v3/testsuite/experimental/memory_resource/new_delete_resource.cc
@@ -23,6 +23,11 @@
 #include <cstdlib>
 #include <testsuite_hooks.h>
 
+#if defined __sun__ && defined __i386__
+// See PR libstdc++/77691
+# define BAD_MAX_ALIGN_T 1
+#endif
+
 bool new_called = false;
 bool delete_called = false;
 std::size_t bytes_allocated = 0;
@@ -38,14 +43,14 @@ void* operator new(std::size_t n)
   throw std::bad_alloc();
 }
 
-void operator delete(void* p)
+void operator delete(void* p) noexcept
 {
   delete_called = true;
   std::free(p);
   bytes_allocated = 0; // assume everything getting deleted
 }
 
-void operator delete(void* p, std::size_t n)
+void operator delete(void* p, std::size_t n) noexcept
 {
   delete_called = true;
   std::free(p);
@@ -55,9 +60,7 @@ void operator delete(void* p, std::size_t n)
 
 template<std::size_t A>
   bool aligned(void* p)
-  {
-    return (reinterpret_cast<std::uintptr_t>(p) % A) == 0;
-  }
+  { return (reinterpret_cast<std::uintptr_t>(p) % A) == 0; }
 
 template<typename T>
   bool aligned(void* p)
@@ -108,13 +111,17 @@ test03()
   using std::size_t;
   void* p = nullptr;
 
-  auto max = [](int n, int a) { return n > a ? n : a; };
+  auto round = [](size_t n, size_t a) { return n % a ? n + a - (n % a) : n; };
 
   bytes_allocated = 0;
 
   memory_resource* r1 = new_delete_resource();
   p = r1->allocate(1); // uses alignment = alignof(max_align_t)
-  VERIFY( bytes_allocated <= alignof(max_align_t) );
+#ifdef BAD_MAX_ALIGN_T
+  VERIFY( bytes_allocated != 0 );
+#else
+  VERIFY( bytes_allocated == alignof(max_align_t) );
+#endif
   VERIFY( aligned<max_align_t>(p) );
   r1->deallocate(p, 1);
   VERIFY( bytes_allocated == 0 );
@@ -123,17 +130,16 @@ test03()
   VERIFY( bytes_allocated == 2 );
   VERIFY( aligned<max_align_t>(p) );
   r1->deallocate(p, 2, alignof(char));
-  __builtin_printf("%d\n", (int)bytes_allocated);
   VERIFY( bytes_allocated == 0 );
 
   p = r1->allocate(3, alignof(short));
-  VERIFY( bytes_allocated == max(3, alignof(short)) );
+  VERIFY( bytes_allocated == round(3, alignof(short)) );
   VERIFY( aligned<short>(p) );
   r1->deallocate(p, 3, alignof(short));
   VERIFY( bytes_allocated == 0 );
 
   p = r1->allocate(4, alignof(long));
-  VERIFY( bytes_allocated == max(4, alignof(long)) );
+  VERIFY( bytes_allocated == round(4, alignof(long)) );
   VERIFY( aligned<long>(p) );
   r1->deallocate(p, 4, alignof(long));
   VERIFY( bytes_allocated == 0 );
diff --git a/libstdc++-v3/testsuite/experimental/memory_resource/resource_adaptor.cc b/libstdc++-v3/testsuite/experimental/memory_resource/resource_adaptor.cc
index 27ee107..56c8ffa 100644
--- a/libstdc++-v3/testsuite/experimental/memory_resource/resource_adaptor.cc
+++ b/libstdc++-v3/testsuite/experimental/memory_resource/resource_adaptor.cc
@@ -1,6 +1,5 @@
 // { dg-do run { target c++14 } }
 // { dg-require-cstdint "" }
-// { dg-xfail-run-if "PR libstdc++/77691" { { i?86-*-solaris2.* x86_64-*-solaris2.* } && ilp32 } }
 
 // Copyright (C) 2016-2019 Free Software Foundation, Inc.
 //